<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        function changeCode() {
            var imgObj = document.getElementById("codeImg");
            imgObj.src = "/checkCode?" + Math.random();
        }
    </script>
</head>
<body>
    <form action="/session/checkUser">
        验证码：<img src="/checkCode" id="codeImg">
        <a href="javascript:changeCode()">看不清楚换一张</a><br>
        请输入验证码：<input type="text" name="userCode"><br>
        <input type="submit" value="提交">
    </form>
</body>
</html>